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Date: Sat, 30 Mar 2024 22:43:02 -0700
From: syzbot <syzbot+1fa663a2100308ab6eab@...kaller.appspotmail.com>
To: hdanton@...a.com, linux-kernel@...r.kernel.org,
syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [bpf?] possible deadlock in kvfree_call_rcu
Hello,
syzbot has tested the proposed patch but the reproducer is still triggering an issue:
possible deadlock in hrtimer_start_range_ns
======================================================
WARNING: possible circular locking dependency detected
6.8.0-syzkaller-08951-gfe46a7dd189e-dirty #0 Not tainted
------------------------------------------------------
syz-executor.0/5489 is trying to acquire lock:
ffff8880b952c8d8 (hrtimer_bases.lock){-.-.}-{2:2}, at: lock_hrtimer_base kernel/time/hrtimer.c:175 [inline]
ffff8880b952c8d8 (hrtimer_bases.lock){-.-.}-{2:2}, at: hrtimer_start_range_ns+0xdf/0xc60 kernel/time/hrtimer.c:1303
but task is already holding lock:
ffff88802195e9f8 (&trie->lock){-.-.}-{2:2}, at: trie_update_elem+0xcb/0xc10 kernel/bpf/lpm_trie.c:324
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (&trie->lock){-.-.}-{2:2}:
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
trie_delete_elem+0x96/0x6a0 kernel/bpf/lpm_trie.c:451
0xffffffffa00060ce
bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
__bpf_prog_run include/linux/filter.h:657 [inline]
bpf_prog_run include/linux/filter.h:664 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline]
bpf_trace_run2+0x204/0x420 kernel/trace/bpf_trace.c:2420
trace_hrtimer_start include/trace/events/timer.h:222 [inline]
debug_activate kernel/time/hrtimer.c:479 [inline]
enqueue_hrtimer+0x335/0x3a0 kernel/time/hrtimer.c:1090
__hrtimer_start_range_ns kernel/time/hrtimer.c:1265 [inline]
hrtimer_start_range_ns+0xaa0/0xc60 kernel/time/hrtimer.c:1305
futex_wait_queue+0xb0/0x1d0 kernel/futex/waitwake.c:357
__futex_wait+0x17f/0x320 kernel/futex/waitwake.c:669
futex_wait+0x101/0x360 kernel/futex/waitwake.c:697
do_futex+0x33b/0x560 kernel/futex/syscalls.c:102
__do_sys_futex kernel/futex/syscalls.c:179 [inline]
__se_sys_futex+0x3f9/0x480 kernel/futex/syscalls.c:160
do_syscall_64+0xfb/0x240
entry_SYSCALL_64_after_hwframe+0x6d/0x75
-> #0 (hrtimer_bases.lock){-.-.}-{2:2}:
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
__lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
lock_hrtimer_base kernel/time/hrtimer.c:175 [inline]
hrtimer_start_range_ns+0xdf/0xc60 kernel/time/hrtimer.c:1303
hrtimer_start include/linux/hrtimer.h:275 [inline]
run_page_cache_worker kernel/rcu/tree.c:3342 [inline]
kvfree_call_rcu+0x60e/0x7c0 kernel/rcu/tree.c:3447
trie_update_elem+0x819/0xc10 kernel/bpf/lpm_trie.c:385
bpf_map_update_value+0x4d3/0x540 kernel/bpf/syscall.c:203
generic_map_update_batch+0x60d/0x900 kernel/bpf/syscall.c:1876
bpf_map_do_batch+0x3e0/0x690 kernel/bpf/syscall.c:5145
__sys_bpf+0x377/0x810
__do_sys_bpf kernel/bpf/syscall.c:5738 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5736 [inline]
__x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5736
do_syscall_64+0xfb/0x240
entry_SYSCALL_64_after_hwframe+0x6d/0x75
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&trie->lock);
lock(hrtimer_bases.lock);
lock(&trie->lock);
lock(hrtimer_bases.lock);
*** DEADLOCK ***
3 locks held by syz-executor.0/5489:
#0: ffffffff8e132020 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:298 [inline]
#0: ffffffff8e132020 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:750 [inline]
#0: ffffffff8e132020 (rcu_read_lock){....}-{1:2}, at: bpf_map_update_value+0x3c4/0x540 kernel/bpf/syscall.c:202
#1: ffff88802195e9f8 (&trie->lock){-.-.}-{2:2}, at: trie_update_elem+0xcb/0xc10 kernel/bpf/lpm_trie.c:324
#2: ffff8880b9529470 (krc.lock){....}-{2:2}, at: krc_this_cpu_lock kernel/rcu/tree.c:2960 [inline]
#2: ffff8880b9529470 (krc.lock){....}-{2:2}, at: add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3360 [inline]
#2: ffff8880b9529470 (krc.lock){....}-{2:2}, at: kvfree_call_rcu+0x192/0x7c0 kernel/rcu/tree.c:3445
stack backtrace:
CPU: 1 PID: 5489 Comm: syz-executor.0 Not tainted 6.8.0-syzkaller-08951-gfe46a7dd189e-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2187
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
__lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
lock_hrtimer_base kernel/time/hrtimer.c:175 [inline]
hrtimer_start_range_ns+0xdf/0xc60 kernel/time/hrtimer.c:1303
hrtimer_start include/linux/hrtimer.h:275 [inline]
run_page_cache_worker kernel/rcu/tree.c:3342 [inline]
kvfree_call_rcu+0x60e/0x7c0 kernel/rcu/tree.c:3447
trie_update_elem+0x819/0xc10 kernel/bpf/lpm_trie.c:385
bpf_map_update_value+0x4d3/0x540 kernel/bpf/syscall.c:203
generic_map_update_batch+0x60d/0x900 kernel/bpf/syscall.c:1876
bpf_map_do_batch+0x3e0/0x690 kernel/bpf/syscall.c:5145
__sys_bpf+0x377/0x810
__do_sys_bpf kernel/bpf/syscall.c:5738 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5736 [inline]
__x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5736
do_syscall_64+0xfb/0x240
entry_SYSCALL_64_after_hwframe+0x6d/0x75
RIP: 0033:0x7f44a5a7dda9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f44a686a0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007f44a5babf80 RCX: 00007f44a5a7dda9
RDX: 0000000000000038 RSI: 0000000020000000 RDI: 000000000000001a
RBP: 00007f44a5aca47a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f44a5babf80 R15: 00007ffc1ffeb058
</TASK>
Tested on:
commit: fe46a7dd Merge tag 'sound-6.9-rc1' of git://git.kernel..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=148dffe6180000
kernel config: https://syzkaller.appspot.com/x/.config?x=fe78468a74fdc3b7
dashboard link: https://syzkaller.appspot.com/bug?extid=1fa663a2100308ab6eab
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch: https://syzkaller.appspot.com/x/patch.diff?x=15a5ffe6180000
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